The general objectives are the understanding of the hearing processes in man and animals under normal and abnormal conditions. The specific objectives are the study of these processes in the lowermost vertebrates, the amphibians and teleost fishes, so as to reveal more clearly the differences in these forms from the higher types of ears of reptiles, birds, and mammals. The methods of investigation include: (1) the recording of electrophysiological responses of the ear during stimulation with sounds and (2) the examination of auditory structures by dissection and by advanced histological techniques that reveal the tectorial tissues and their relations to the auditory hair cells. The results will be brought to bear on questions of evolutionary development within the vertebrate series.